Copolymer-type pigment dispersing agents have been developed in a variety of fields.
In the field of top coats for automotive finish, a pigment dispersion resin capable of providing an aqueous pigment dispersion that has, for example, low viscosity even at a high pigment concentration and is good at chromogenic properties as well as good in finished appearance and film performances of a coated film has been developed. Patent Document 1 describes a resin having a weight average molecular weight within a range of 3,000 to 100,000 obtained through copolymerization, performed in the presence of a radical polymerization initiator, of a monomer mixture consisting of a macromonomer (A) obtained by polymerizing monomer components consisting of at least one polymerizable monomer selected from methacrylic esters and styrene, and methacrylic acid if necessary, in the presence of a metal complex working as a catalytic chain transfer agent or an addition fragmentation chain transfer agent, and a radical polymerization initiator if necessary, a polymerizable unsaturated monomer (B) containing at least one ionic functional group selected from an amino group, a quaternary ammonium base and a sulfonic group, a non-ionic polymerizable unsaturated monomer (C) having a polyoxyalkylene chain, and another ethylenically unsaturated monomer (D). Specifically, it describes, for example, a copolymer obtained through polymerization of a macromonomer prepared from methyl methacrylate and methacrylic acid with styrene, methyl methacrylate, n-butyl methacrylate, 2-hydroxyethyl methacrylate, dimethylaminoethyl methacrylate and polyethylene glycol monomethacrylate.
Alternatively, in the fields of coatings, inks, building materials and the like, pigment dispersing agents minimally containing a volatile organic compound have been developed. Patent Document 2 describes, as a pigment dispersing agent minimally containing a volatile organic compound, a copolymer composed of an aromatic and/or heterocyclic vinyl monomer unit (a), a monomer unit (b) having an acid group, a (meth)acrylic acid ester monomer unit (c), and a monomer unit (d) having a polyalkylene (the alkylene having 2 to 6 carbon atoms) glycol chain having a number average molecular weight of 150 to 1500 or having a monoalkyl (the alkyl having 1 to 22 carbon atoms) ether chain of the glycol. Specifically, it describes, for example, a random copolymer of styrene, methyl methacrylate, ethyl methacrylate, methacrylic acid and PEG monomethyl ether methacrylate.
Alternatively, in the field of color liquid crystal displays, a pigment dispersion for a color filter used for manufacturing an optical color filter has been developed. In Patent Document 3, a block copolymer consisting of a pigment adsorbing block containing a basic group as a pigment adsorbing group and a block containing no pigment adsorbing group is used as a pigment dispersing agent for a color filter. Specifically, a block copolymer (Disperbyk-2001 manufactured by BYK Japan KK) consisting of a pigment adsorbing block containing a pigment adsorbing group with an amine number of 26 and an acid number of 18 and a block containing no pigment adsorbing group is used.